Optics for medical laser

ABSTRACT

A visible helium neon beam is used as an aiming beam to establish a spot at which a carbon dioxide beam also focuses. The carbon dioxide beam is then employed to vaporize biotic material. A distal end of an articulated arm may couple with the micromanipulator to direct the carbon dioxide beam from the laser through a waveguide and into the micromanipulator. Another aspect of the invention includes introducing the aiming beam into the waveguide through a dichroic mirror positioned in a knuckle joint of the articulated arm. In one embodiment, a laser diode generates the visible light of the aiming beam, and is disposed proximate to the distal end of the articulated arm.

This application is a division of application Ser. No. 07/644,074, filedJan. 18, 1991 now U.S. Pat. No. 5,198,926.

FIELD OF THE INVENTION

The present invention relates generally to the field of optics and morespecifically to the field of laser surgery.

BACKGROUND OF THE INVENTION

Materials such as optical glass can be formed as convergent or divergentlenses. One problem inherent in optical lenses is that when two lightbeams having significantly different wavelengths pass through a lensmaterial, they will become focused at different points, due towavelength dispersion. Mathematically, dispersion is defined as the rateof change of the index of refraction (n), with respect to the wavelength(λ) or D=dn/dλ. As different wavelengths are transmitted through thelens, the lens exhibits a different index of refraction for eachwavelength. Thus, different wavelengths are refracted differently, andthereby focus at different points.

This focusing anomaly for greatly differing wavelengths can beundesirable in certain applications, such as laser surgery. Due tocertain desirable properties of laser light outside the visible portionof the spectral range, physicians often perform laser surgery usinglaser light that is invisible to the human eye, e.g., wavelengths in thefar infrared. Because this light cannot be seen by the surgeon, medicallaser systems utilizing invisible light typically employ a low power"aiming" laser beam at a visible wavelength. The aiming beam is focusedon a patient where an incision is to be made, and then a high powerlaser beam at an invisible wavelength is applied to make an incision atthe point where the low powered beam is focused. Typical medical lasersystems employ a helium neon laser, emitting a beam of approximately0.63 microns wavelength which is not damaging to biotic material, forthe low powered aiming beam and a carbon dioxide laser, emitting a beamof approximately 10.6 microns wavelength which vaporizes bioticmaterial, for the high powered cutting beam. The two beams must focus atthe same point to ensure the incision is made at the desired location.Even small differences in the location of the focal points of the beamscan cause the tissue of a patient to be cut improperly.

Achromatic lens elements are commonly used to align the focal point oftwo different wavelengths passing through the same optical system. Suchelements comprise two different materials which, together, correct forthe focusing anomaly caused by dispersion. The different materials ofthe achromatic lens elements have substantially different indices ofrefraction and dispersion relationships such that they focus two beamsof substantially different wavelengths at the same focal point. However,achromats have typically been used within a moderate range ofwavelengths since it is difficult to find two materials whichachromatically focus and transmit light over a large wavelengthseparation. The choices of materials are limited not only by achromaticcompatibility, but by absorption properties. Typical optical glasses,for example, do not transmit well at wavelengths approaching 2.7 micronsor more due to strong water absorption peaks in the vicinity of threemicrons. These problems have severely restricted the use of achromats inmedical laser systems.

Accordingly, there is a need in the art for an achromatic opticalelement which will focus widely separated wavelengths, particularlywhere one of the wavelengths is in the visible portion of the opticalspectrum and the other is in the far infrared.

SUMMARY OF THE INVENTION

The present invention comprises an optical system for achromaticallyfocusing light comprised of at least first and second wavelengths suchthat the light at the first wavelength and the light at the secondwavelength are focused substantially at a common location. The opticalsystem comprises an achromatic optical element formed by at least firstand second materials, the first and second materials having differentdispersions. Both of the first and second materials are transmissive tothe first and second wavelengths, the first wavelength being in thevisible portion of the optical spectrum and the second wavelength beingin the infrared portion of the optical spectrum and being on the orderof about two and one-half microns or greater.

In the preferred embodiment, the optical element comprises a first lensand a second lens, the first lens being comprised of the first materialand the second lens being comprised of the second material. The firstmaterial preferably comprises potassium chloride and the second materialpreferably comprises zinc selenide. The lenses may be mounted with anair space therebetween and are preferably arranged such that the lightpasses through the first material before passing through the secondmaterial. The first lens may comprise a positive bi-convex lens and thesecond lens may comprise a negative meniscus lens, thereby forming apositive doublet lens. Additionally the optical system may comprise asecond optical element which comprises a negative singlet lens. Thenegative singlet lens and the positive doublet lens may be arrangedsubstantially in a Galilean telescope configuration, wherein the singletlens has a principal axis and the doublet lens has a principal axis, theaxes being aligned along a propagation path of the light of the firstand second wavelengths.

The achromatic optical element is preferably mounted in amicromanipulator. The light of the second wavelength may be ofsufficiently high intensity to vaporize biotic material, such as tissue,and may be produced by a carbon dioxide laser having a wavelength of10.6 microns. The light of the first wavelength may be of sufficientlylow intensity that the biotic material is substantially unaffected bythe light of the first wavelength, and may be produced by a helium neonlaser having a wavelength of 632.8 nanometers.

In accordance with another aspect of the present invention, anachromatic optical element comprises a first lens of potassium chlorideand a second lens of zinc selenide. The achromatic optical elementpreferably consists of a doublet lens, and the first and second lensesmay be juxtaposed with an air gap therebetween. A micromanipulatorhaving a housing with an input portion for receiving light and an outputportion for outputting light may be utilized to mount the opticalelement. The lenses are mounted such that light from the input portionpasses through the first lens before passing through the second lens.The housing preferably comprises manipulator controls for controllingthe direction and focal point of light propagating through the outputportion.

The present invention also encompasses a method of focusing an invisiblelaser light beam having a wavelength of about two and one-half micronsor more and a visible aiming light beam. The method comprises passingboth the visible and invisible beams through an achromatic opticalelement such that the visible and invisible beams are focused at acommon location.

A method of manufacturing an optical apparatus which is encompassed bythe present invention comprises mounting plural lenses to form anachromatic optical element and selecting materials for the lenses whichtransmit both light having a wavelength in the visible portion of theoptical spectrum and light having a wavelength of about three microns ormore. In this method, the step of selecting materials preferablycomprises the step of selecting potassium chloride for one of the lensesand the step of selecting zinc selenide for another of the lenses.

In accordance with another aspect of the invention, the apparatus fordelivery of laser energy for a laser surgery system comprises anarticulated arm including a waveguide directing the propagation of laserlight and at least one knuckle joint. The knuckle joint has a dichroicmirror to change the direction of the propagating laser light byreflecting substantially all of the laser light. The apparatus furthercomprises a visible light source, such as a helium neon laser, whichemits visible light at about 633 nanometers; or a laser diode whichemits visible light having a wavelength of about 670 nanometers.Assembled with the arm, the visible light source is disposed proximateto the distal end of the articulated arm and positioned to introducevisible light into the waveguide through the dichroic mirror at theknuckle joint for the purpose of providing an aiming beam. In thepreferred embodiment, the laser light is produced by a carbon dioxidelaser and its axis of propagation aligns with the aiming beam axis ofpropagation when the visible light is introduced into the waveguide.

In accordance with another aspect of the invention, the apparatus fordelivery of laser energy for a laser surgery system comprises a lasersource emitting laser light, a waveguide linkage directing the laserlight along an axis of propagation, a dichromic mirror reflecting thelaser light to change the direction of the axis of propagation and alaser diode emitting visible light. A plurality of coupled waveguidesegments forms the waveguide linkage. In assembly, the laser diode isdisposed proximate to a distal end of the waveguide linkage and ispositioned such that visible light passes through the dichroic mirror tocouple with the axis of propagation of the laser light. Preferably, theapparatus additionally comprises at least one knuckle joint housing thedichroic mirror.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a medical laser apparatus having a micromanipulatormounted on a colposcope and stand to be used for gynecological lasersurgery and connected to an articulated arm.

FIG. 2 illustrates an alternative embodiment of the apparatus shown inFIG. 1.

FIG. 3 is an enlarged view of the knuckle joint/beam combiner assemblyshown in FIG. 2 relieved to show a laser diode assembly and internalstructure of joint/beam combiner.

FIG. 4 is an enlarged view of the micromanipulator mounted on thecolposcope.

FIG. 5 is an exploded view of the micromanipulator.

FIG. 6 shows a cross-sectional view of the optical housing of themicromanipulator, taken along line 6--6 in FIG. 5.

FIG. 7 is a schematic view of the optical system of the presentinvention.

FIG. 8 is an enlarged schematic view of a second end of the opticalsystem of the present invention. Both a visible aiming beam and aninvisible laser beam are schematically shown propagating through theoptical system.

DETAILED DESCRIPTION OF THE INVENTION

Medical lasers are used in surgery to allow a surgeon to direct a highpowered laser beam, capable of vaporizing biotic material, to a precisearea on a patient. First, a low power laser beam is aimed at and focusedon biotic material, such as tissue. Then, a high power laser beam, whichfocuses at the same point as the low power aiming beam, is energized tovaporize the biotic material. It is necessary that the two beams focusat the same point so that the incision is made accurately.

FIG. 1 illustrates a micromanipulator system mounted on a stand 10 foruse in gynecological surgery. A colposcope 12, or surgical microscope,is mounted on a mounting block 14 which rests atop a rotatable platform16 at the top of the stand 10. The mounting block 14 has counter sunkholes (not shown) at a forward end 14a. A maneuvering lever 18 extendsfrom just beneath the rotatable platform 16. The colposcope 12 has twoadjacent eyepieces 20. An illuminator 22 is located above and betweenthe adjacent eyepieces 20.

A micromanipulator 30, having a housing made of a material such asmetal, is supported on the colposcope 12 via a generally bell-shapedorifice 32 (shown in FIG. 4) in the housing. An articulated arm 34 isattached, via a coupling mechanism 94 (shown in FIG. 5), to a lower endof the micromanipulator 30 having a generally cylindrical pilot 31(shown in FIG. 5) with a hollow center protruding from a collet 36.

As shown in FIG. 1, the articulated arm 34 comprises a linkage ofwaveguide segments 35 for directing laser light along an axis ofpropagation 37 (FIG. 3) with a proximal end 39 of the articulated arm 34connected to a laser source 40 via a quick release connector 42. As usedherein, the words proximal and distal are used in reference to proximityof the laser 40 which supplies laser light to the waveguide 35.Preferably, the articulated arm 34 connects to a carbon dioxide laser.The waveguide segments 35 preferably comprise a hollow core ceramictube.

The articulated arm 34 additionally comprises a plurality of knucklejoints 38 which link the waveguide segments 35 together. Each knucklejoint 38 comprises a set of bearings 41 (FIG. 3) which allows a firstwaveguide segment to rotate relative to a second waveguide segment. Theknuckle joint 38 further comprises a mirror 43 (FIG. 3) which directslight from the second segment into the first segment by reflection andthereby changes the direction of the axis of propagation 37.

The articulated arm 34 further includes a beam combiner 44, shown inFIG. 1, which mounts on the articulated arm 34 near the micromanipulator30. A low-powered, helium neon laser 46 is coupled into the beamcombiner 44 via a fiber-optic waveguide 48, thereby combining thevisible helium neon beam and the invisible carbon dioxide beam prior toentry into the micromanipulator 30. Examples of articulated arms aredisclosed in U.S. Pat. Nos. 4,917,083 and 4,583,539. The beam combiner44 may comprise a dichroic mirror mounted in the arm in manner disclosedin U.S. Pat. No. 4,917,083. These patents are incorporated herein byreference.

FIGS. 2 and 3 show an alternative preferred embodiment of thearticulated arm 34a. Where appropriate, like numbers with an "a" suffixhave been used to indicate like parts between the two embodiments forease of understanding. The articulated arm 34a comprises a waveguidelinkage 35a, a plurality of knuckle joints 38a, and a visible lightsource 57. One of the knuckle joints comprises a novel a knucklejoint/beam combiner 47, which permits the visible aiming beam to beintroduced into the articulated arm through a knuckle joint. The visiblelight source shown in FIGS. 2 and 3 comprises a laser diode assembly 45.It will be understood, however, that other light sources, such as ahelium neon laser, may be used alternatively. However, use of a laserdiode reduces costs and produces a more completely integratedarticulated arm 34a.

Referring to FIG. 3, the laser diode assembly 45 comprises a laser diode49 (such as a Toshiba 10 milli-watt laser diode, part no. 1915) whichemits visible light having a wavelength on the order of 670 nanometers,a 12 volt power supply 51 (available, e.g., from Power Technology, aspart no. 25-4) for powering the laser diode 49, an adjustablecollimating lens 53 (such as a Corning molded aspheric lens, part no.350,150) and an adjustable focusing lens 55 (such as a Corning moldedaspheric lens, part no. 350,170). In assembly, the laser diode 49 plugsinto the power supply 51 which in turn connects to a 12 volt powersupply of a laser source 40a by a pair of electrical leads (not shown).The collimating lens 53 is positioned proximate to the output side ofthe laser diode 49 and the focusing lens 55 is positioned proximate tothe output side of the collimating lens 53. The lenses 53, 55 of thelaser diode assembly 45 are adjusted to produce a focused beam ofvisible light.

The knuckle joint/beam combiner 47 comprises a casing 59 and a set ofbearings 41a, housed in the casing 59, which allows a first waveguidesegment to rotate relative to a second segment. The joint/combiner 47further comprises a dichroic mirror 43a, housed in the casing 59, whichreflects the carbon dioxide laser beam from the second waveguide segmentinto the first waveguide segment and transmits the visible light beam.The joint/combiner 47 additionally comprises a mirror 61 which reflectsthe visible light beam emitted by the laser diode 49 through an aperture63 in the joint/combiner 47 and onto the dichroic mirror 43a.

In assembly, the joint/combiner 47 is disposed proximate to a distal end65 of the articulated arm 34a. The laser diode assembly 45 in turn boltsto the joint/combiner 47 and is positioned such that the visible lightbeam strikes the reflective mirror 61 of the joint/combiner 47.

Introducing the aiming beam at the distal end of the waveguidealleviates alignment problems between the aiming beam and the laserlight. Such alignment problems typically occur because of flexure in thewaveguide segments. Because the wavelength of the visible light is tooshort to be guided by the waveguide, the visible aiming beam propagatesthrough the articulated arm by free space transmission. Thus, if anyflexure occurs in the waveguide segments, the aiming beam is susceptibleto becoming misaligned with the laser light. By introducing the aimingbeam at the distal end of the articulated arm, the aiming beam has lessdistance to travel before it reaches an output end of the articulatedarm, and thus, misalignment errors do not have an opportunity toaccumulate. Further, by eliminating flexure as a source of alignmenterrors, more flexure in the waveguide can be tolerated, and thus, thearm can be structured of lighter less expensive material.

In the power up state, the laser light emitted from a segments 35a. Thiscarbon dioxide laser beam reflects off of the dichroic mirror 43a of theknuckle joint/beam combiner 47 thereby changing its direction ofpropagation. The laser diode emits a divergent cone of visible lightwhich passes through the collimating lens 53 and the focusing lens 55and strikes the surface of the reflective mirror 61. Prior to strikingthe reflective mirror 61, the visible light beam propagates along anaxis which is substantially parallel to the waveguide segment 35a.

The visible light beam reflects off the mirror 61 in a direction passingthrough the joint aperture 63 and striking the dichroic mirror 43a. Thevisible light transmits through the dichroic mirror 43a and into thewaveguide 35a. the visible light transmits through the dichroic mirror43a, an axis of propagation 67 of the visible light aiming beam alignswith the axis of propagation 37a of the laser light. In this manner, thevisible light is coupled into the waveguide for propagation along theaxis of propagation 37a of the carbon dioxide beam. As a result ofreplacing mirror 43 of the normal knuckle joint 38 with the dichroicmirror 43a, a mirror is eliminated from the articulated arm 34 therebysimplifying the assembly and reducing cost.

Referring to FIGS. 4 and 5, a perspective view of the micromanipulator30, as mounted on the colposcope 12, and an exploded view of themicromanipulator 30, respectively, are shown. The micromanipulatorhousing is separable into two parts, a mounting segment 50 and anoptical housing 52. When the mounting segment 50 and optical housing 52are assembled, as in FIG. 4, the optical housing 52 is aligned at aslight angle from the mounting segment 50. Two blind threaded holes (notshown) are located at a first end 50a of the mounting segment. Theseblind holes align with the counter sunk holes (not shown) located at theforward edge of the mounting block 14. Two screws 54 extend through theapertures and the orifices and secure the micromanipulator 30 to themounting block 14.

A generally cylindrical ball housing 56, located just below a second end50b of the mounting segment 50, protrudes from a rear wall 50c of themounting segment 50. A control toggle 58 protrudes from the ball housing56. The toggle 58 is connected via a ball joint 60 to a set 69 of leversand ball joints (shown in FIG. 5) that terminate in a cantileveredmirror arm 62 which extends in the orifice 32 between forward ends 20aof the two eyepieces 20 when the micromanipulator 30 is mounted on thecolposcope 12. A mirror 64 is affixed at an angle to the end of themirror arm 62. The mirror 64 rests above a generally square aperture 68in the first end 50a of the mounting segment 50.

An upper wall 52a of the optical housing 52 is affixed to the first end50a of the mounting segment 50 via four screws 70 which are threadedlyinserted into four counter bored holes 72 (shown in FIG. 5) in theoptical housing 52. These counter bored holes 72 are aligned with fourthreaded holes (not shown) in the first end 50a of the mounting segment50. Two of the counter bored holes 72 in the upper wall 52a of theoptical housing 52 are located on a shoulder 74 protruding from agenerally cubic section 76 of the optical housing. A lens retainer ring78, holding a slightly recessed lens 140, extends from the center of agenerally rectangular recess 82 located in the first end 52a of theoptical housing. The lens retainer ring 78 is ingressive upon thegenerally square aperture 68 in the lower wall 50a of the mountingsegment 50 when the mounting segment 50 and the optical housing 52 areassembled.

A generally cylindrical housing 84, from which protrudes a secondgenerally cylindrical housing 86 having a slightly smaller diameter,extends from the generally cubic section 76 of the optical housing 52.There is a slot 88 located on a first side 52c of the second cylindricalhousing 86. A lever 90 protrudes from the slot 88 and is movable alongthe axis of the slot 88. A generally cylindrical knurled sleeve 92 ismounted coaxially on the second cylindrical housing 86. The sleeve 92 isrotatable about a central axis. The collet 36, having a smaller diameterthan the second cylindrical housing 86, is attached to a lower end ofthe second cylindrical housing 86 and protrudes from the knurled sleeve92. The collet 36 connects with the pilot 31 which, in turn, connectswith the end of the articulated arm 34 having the coupling mechanism 94(as shown in FIG. 5).

Referring to FIG. 6, a cross section, along line 6--6 in FIG. 5, of theoptical housing 52 of the micromanipulator 30 is shown. The pilot 31 andcollet 36 have a relatively large passage 100 that leads to the interiorof a second end 52b of the optical housing, through a snap ring 102 anda lens retainer 104. A negative singlet lens 106, preferably made ofzinc selenide, is held by the lens retainer 104 on one side and anO-ring 108 on the other side. A central axis of the passage 100 and thecenter of the negative lens 106 define an optical axis 110.

The lens retainer 104 is supported by a lens carrier 112. The lenscarrier 112 is encased by a lens carrier housing 114 in which a helicalslide 116 is embedded. A helical slide retainer 118 is located adjacentthe helical slide 116, near the second end 52b of the optical housing52. Sidewalls 120 of the optical housing 52 encase the lens carrierhousing 114. Three clamping screws 122 (only one is shown), located onthe first side 52c of the optical housing, are threadedly inserted intoa portion of the sidewalls 120 of the optical housing 52. A head of eachclamping screw 122 is located within a recess in one of three positionstops 124 (only one is shown). The three position stops 124 and clampingscrews 122 are aligned along a circumference of a circle in a planeperpendicular to the optical axis 110. A drive pin 126 is threadedlyinserted into the lens carrier 112 on a second side 52d of the opticalhousing 52 which is opposite the first side 52c. A head of the drive pin126 rests in a helical slot 127 cut into the surface of the helicalslide 116.

One end of a focusing lever 128, located on the first side of theoptical housing 52, rests within a long, narrow slot 130 arrangedparallel to the optical axis 110. An opposite end of the focusing lever128 is threadedly inserted into a drive ring 132. The drive ring 132 isunder tension of a spring 134. The cylindrical knurled sleeve 92 encasesthe drive ring 132. A connector 136, e.g., a flat head screw, located onthe second side 52d of the optical housing 52, threadedly couples thedrive ring 132 and the knurled sleeve 92 via a tapped hole 138 in thedrive ring 132.

Spaced from the first negative lens 106 along the optical axis 110 is asecond optical element comprising a doublet lens 140. The doublet 140preferably comprises a positive bi-convex lens 142 of potassium chlorideand a negative meniscus lens 144 of zinc selenide. The bi-convex lens142 is aligned closest to the negative lens 106, spaced betweenapproximately 56 and 62 and one-half mm away. There is a small air gap146 of approximately 1 mm (0.972 mm for the preferred embodiment)between the bi-convex lens 142 and the negative meniscus lens 144.

The doublet 140 is held by a lens seating ring 152 having two flexiblelens retaining tabs 150. The lens seating ring 152 is mounted onto alens carrier shaft 154. An end of the lens carrier shaft 154 issurrounded by the lens carrier housing 114. A connector flange 156 and aclamp 158 encase the portion of the lens carrier housing 114 whichsurrounds the lens carrier shaft 154. This, in turn, is encased by thegenerally cubic portion 76 of the optical housing 52 which comprise thefour counter bored holes 72 and four mounting screws 70 and couple theoptical housing 52 to the mounting segment 50. Two of the mountingscrews 70 are shown in FIG. 6.

The lens carrier housing 114 contains a second helical slide 160 nearthe second end of the lens carrier shaft 154. A second drive pin 162 isthreadedly inserted into a portion of the lens carrier shaft 154 and isguided along a helical slot 164 in the second helical slide 160. Thesecond focusing lever 90 is threadedly inserted into the second helicalslide 160, its head protruding on the first side 52c of the opticalhousing 52 through the slot 88 which is aligned perpendicular to theoptical axis 110, as shown in FIGS. 4 and 5.

None of the hardware which support optical elements ingress into thepath of the optical elements. Thus, light entering the optical housing52 through the passage 100 can travel through the optical housing 52without significant aperture stoppage.

Referring to FIGS. 7 and 8, a schematic view of the optical systemremoved from the optical housing 52 of the micromanipulator 30 is shown.Due to size limitations in the drawings, the helium neon and carbondioxide wavelengths are depicted with only a single set of light rays inFIG. 7. However, it will be understood that both of these wavelengthspropagate through the optical system of FIG. 7 and both are incident onthe three lenses 106, 142, and 144. In FIG. 8, a schematic, enlargedview of a portion of the first end 52a of the optical system is shown,illustrating the helium neon and carbon dioxide beams slightlyseparated.

The negative lens 106 is located at the second end of the opticalhousing, approximately 25 mm away from the nearest edge of the collet 36(shown in FIG. 6). As described previously, the central axis of thecollet 36 and the center of the negative lens 106 form an optical axis110. Between approximately 56 mm and 62 and one-half mm away on theoptical axis from the initial negative lens 106, is the doublet 140. Thedoublet 140 comprises the bi-convex lens 142 and the negative meniscuslens 144, with the approximately one mm air gap 146 (0.972 mm for thepreferred embodiment) in between the two elements. The doublet 140 isarranged such that incident laser light contacts the bi-convex elementfirst 142. Light transmitted through the bi-convex element 142 isincident on the approximately one millimeter wide air gap 146 (i.e.,0.972 mm for the preferred embodiment), which transmits light to thenegative meniscus lens element 144. Light transmitted by the negativemeniscus lens 144 is incident on the mirror 64 which is also aligned onthe optical axis 110 and is mounted on the mirror arm 62 within thebell-shaped orifice 32 in the mounting segment 50.

The table below defines the micromanipulator lens specifications for thepreferred embodiment of the present invention. Each of the opticalelements 106, 142, and 144 have a slight protective bevel. Additionally,the zinc selenide elements 106 and 144 are coated with an antireflectioncoating of reflectivity equal to or less than 0.5%.

    ______________________________________                                              Radius of               Center                                          Lens  Curvature      Diameter Thickness                                       No.   R.sub.1  R.sub.2   (mm)   (mm)    Mat'l.                                ______________________________________                                        106   -9.524   plano     10     0.979   ZnSe                                  142   26.615   -18.149   17.8   5.509   KCl                                   144   -17.43   -26.057   17.8   1.874   ZnSe                                  ______________________________________                                    

The index of refraction of zinc selenide ranges from approximately 2.4to 2.6, while the index of refraction for potassium chloride ranges from1.45 to 1.48. The average dispersions of the optical elements are asfollows: 0.19 for the initial negative lens 106; 0.03 for the bi-convexlens 142; and 0.19 for the negative meniscus 144.

The potassium chloride bi-convex lens 142 is highly susceptible todamage induced by liquid, as salts are generally dissolved by liquids,including vapor or blood. However, a moisture protective coating for10.6 microns and 0.63 microns wavelength protects the potassium chloridelens 142. Additionally, the advantageous placement of the zinc selenidenegative meniscus lens 149 closer to the first end 52a of the opticalhousing 52 helps to protect the potassium chloride lens 142 fromsplashes during surgery. Thus, the potassium chloride lens 142 is wellprotected within the optical housing 52, ensuring that themicromanipulator 30 of the present invention provides accurate placementof the carbon dioxide cutting beam.

The micromanipulator 30 illustrated in FIGS. 1, 2, and 4 is mountedespecially for use in gynecological surgery. However, the opticalhousing 52 can be coupled with a different mounting segment formed tofit over other surgical viewing elements, such as an operatingmicroscope. Thus, the micromanipulator 30 of the present invention mayalso be used in other types of laser surgery.

The colposcope 12 (or other surgical viewing instrument) aids in theaccurate placement of the carbon dioxide cutting beam by magnifying thetissue to be vaporized, allowing more accurate focusing of the heliumneon aiming beam's spot, and therefore the cutting beam's spot as well.

The distance between the negative lens 106 and the spot where the twolaser beams come to a focus is defined as the working distance. Bychanging the working distance, a surgeon can regulate the plane in whichtissue is vaporized by the carbon dioxide laser beam. The workingdistance is modified by axially altering the position of the negativelens 106.

The size of the carbon dioxide laser spot in the plane where both thecarbon dioxide and helium neon beams come to a focus is defined as thespot size. By changing the spot size, a surgeon can regulate how largean area of tissue is vaporized. The spot size is modified by axiallyaltering the position of the doublet element 140.

The negative lens 106 is mobile via a focusing mechanism which isinitiated by rotation of the knurled sleeve 92 about its cylindricalaxis. The spring 134 provides tension against the drive ring 132 toyield tautness in the rotation of the knurled sleeve 92. Since theknurled sleeve 92 and the drive ring 132 are coupled via the connector136, the knurled sleeve 92 causes the drive ring 132 to rotate. As thedrive ring 132 rotates, the threadedly inserted focusing lever 128 iscaused to rotate with the drive ring 132. The body of the focusing lever138, held within the long, narrow slot 138 in the helical slide 116,causes the helical slide 116 to rotate. As the helical slide 116rotates, the head of the drive pin 126 is guided within the helical slot127 cut within the helical slide 116. Thus, the drive pin 126 is causedto move axially along the optical axis 110. Since the body of the drivepin 126 is threadedly inserted into the lens carrier 112, the lenscarrier 112 is transported axially. The negative zinc selenide lens 106is thereby moved axially within the optical housing 52, allowingadjustment of the working distance. This method of conversion of therotational motion of the knurled sleeve 92 to translational motion ofthe negative lens 106 allows fine adjustment to be made to axialposition of the lens 106 with relatively large rotational motion of theknurled sleeve 92.

The three position stops 124 on the knurled sleeve 92 are calibratedduring assembly of the optical housing 52. As the drive ring 132 ismoved axially against the tension of the spring 134, the body of thefocusing lever 128 is moved axially within the long narrow slot 130 inthe helical slide 116. When the correct spring tension is established ateach position stop 124, the clamping screw 122 is tightened within theparticular position stop 124. The position stops 124 cause the knurledsleeve 92 to stop rotating about the optical axis 110 until enoughrotational force is applied to overcome the position stop 124. Thus, thethree position stops 124 provide three predetermined working distances.

To change the spot size, the doublet 140 is mobile via a focusingmechanism comprising the second focusing lever 90. When the secondfocusing lever 90 is moved within the slot 88 in which it is positioned,the second helical slide is caused to rotate about the optical axis 110along with the second focusing lever 90. The head of the second drivepin 162 is thereby guided along the helical slot 164 in the secondhelical slide 160. The body of the second drive pin 162 thus movesaxially, causing the lens carrier shaft 154 to move axially. The motionof the lens carrier shaft 154 causes the lens carrier 152 to moveaxially, thereby causing the doublet 140 to be shifted axially.

The spot of the helium neon aiming beam is preferably located within thespot of the carbon dioxide cutting beam for accurate aiming of thecarbon dioxide cutting beam. The micromanipulator 30 of the presentinvention is able to focus both beams accurately even when there aresmall alignment errors. The optical design of the present inventionensures that the helium neon laser spot rests within the carbon dioxidelaser spot even when the beams are incident off the optical axis 110, upto at least three degrees in the same direction.

Although both focusing mechanisms alter the distance between the twolenses, it is more convenient for the surgeon to have separateadjustments for working distance and for spot size. With separateadjustments, the surgeon can determine the working distance and thenadjust the spot size to vaporize a larger or smaller area in the planedetermined by the working distance.

Further providing convenience for the surgeon, the optical housing 52can be mounted such that it is accessible to both right and left handedsurgeons. The optical housing 52 can be attached via the four mountingscrews 70 such that the shoulder 74 is adjacent one side of the mountingsegment 50, as shown in FIG. 5 for example. The optical housing 52 isthen aligned at a small angle from the longitudinal axis of the mountingsegment 50 and the second focusing lever 90 is easily accessible to aright handed surgeon. By rotating the optical housing 52 by 180° duringassembly of the micromanipulator 30, the optical housing 52 can bealigned at a small angle on the other side of the longitudinal axis ofthe mounting segment 50 and the second focusing lever 90 is made easilyaccessible to a left handed surgeon. Thus, the spot size of the beams isambidextrously controllable, depending upon the angular orientation ofthe optical housing 52 with respect to the mounting segment 50.

The surface curvatures of the two lenses 142 and 144 of the doublet 140are adjusted by computer optimization to produce an output beam in whichaberrations are well corrected and the system is limited only bydiffraction. The air space 146 between the two lenses 142 and 144 ishelpful in correcting some aberrations, but is not entirely necessary.The adjacent surfaces of the potassium chloride bi-convex lens 142 andthe zinc selenide negative meniscus 144 lens can be matched and placedin contact with a small loss of beam quality at the helium neonwavelength.

One skilled in the art will realize that the micromanipulator 30 can bemounted on any surgical viewing apparatus by changing the shape of theorifice in the mounting segment 50 to fit over the surgical viewingapparatus. Additionally, one skilled in the art will realize that anytype of focusing mechanism can be employed by the micromanipulator 30 solong as it will change the distance between the negative lens 106 andthe doublet 140 to enable accurate placement and sizing of the laserspot.

Although the preferred embodiment of the achromat has been discussed inreference to an aiming beam comprising helium-neon light having awavelength of 633 nanometers, this preferred embodiment will also workwith wavelengths close to 633 nanometers, such as that produced by alaser diode emitting visible light having a wavelength of 670nanometers. Additionally, modifications of the above describedembodiment can be readily made by those skilled in the art to adapt theoptical elements for any of a variety of visible wavelengths.

What is claimed:
 1. An apparatus for delivery of laser energy for alaser surgery system, comprising:an articulated arm comprising awavelength for propagating laser light and at least one knuckle joint,said knuckle joint having a dichroic mirror to change the direction ofsaid propagating laser light by reflecting substantially all of saidlaser light, said knuckle joint disposed proximate to a distal end ofsaid articulated arm; and a visible light source to provide an aimingbeam, said visible light source positioned to introduce said visiblelight into said waveguide through said dichroic mirror at said knucklejoint.
 2. The apparatus of claim 1, wherein said visible light source isa laser diode.
 3. The apparatus of claim 2, wherein said aiming beam hasa wavelength of about 670 nanometers.
 4. The apparatus of claim 2,wherein said laser diode is positioned such that said visible lightpropagates substantially parallel to said waveguide prior to saidvisible light being introduced into said waveguide.
 5. The apparatus ofclaim 1, wherein said visible light source is a helium neon laser. 6.The apparatus of claim 1, wherein said laser light is produced by acarbon dioxide laser.
 7. The apparatus of claim 1, additionallycomprising a mirror to reflect said visible light onto said dichroicmirror.
 8. The apparatus of claim 1, wherein said visible light isintroduced into said waveguide such that an axis of propagation of saidaiming beam is aligned with an axis of propagation of said laser light.9. The apparatus of claim 1, additionally comprising a collimating lens.10. The apparatus of claim 1, additionally comprising a focusing lens.11. An apparatus for delivery of laser energy for a laser surgerysystem, comprising:a laser source for emitting invisible light having afirst wavelength; a waveguide linkage for directing said invisible lightalong an axis of propagation, said linkage formed by a plurality ofcoupled waveguide segments; a laser diode for emitting visible lighthaving a second wavelength; and a dichroic mirror in said waveguidelinkage for reflecting light of one of said wavelengths whiletransmitting light of another of said wavelengths, said diode disposedproximate to a distal end of said waveguide linkage and positioned suchthat said visible light is received by said dichroic mirror to combinethe visible and invisible light for propagation along said axis ofpropagation.
 12. The apparatus of claim 11, additionally comprising atleast one knuckle joint, wherein said dichroic mirror is disposed atsaid knuckle joint.
 13. The apparatus of the claim 11, additionallycomprising plural lenses mounted to receive light from said waveguidelinkage, one of said lenses consisting of potassium chloride and anotherof said lenses consisting of zinc selenide.